1. Field of the Invention
The present invention relates to a volume homeostatic fluid--fluid exchanger which can facilitate the clearance of post-vitrectomy vitreous hemorrhage. The present invention also relates to a new method for managing the recurrent vitreous hemorrhage in proliferative diabetic retinopathy after posterior vitrectomy.
2. Description of the Related Art
A number of methods for performing a vitrectomy have heretofore been disclosed, an example of which is disclosed U.S. Pat. No. 5,304,118 to Trese et al, incorporated herein for reference. The management of proliferative diabetic retinopathy (PDR) is very difficult. Despite the successful posterior vitrectomy with complete membrane peeling, the incidence of post-operation recurrent hemorrhage is relatively high, up to 29% to 75% (Mieler W F, Wolf M D. In: Lewis H, Ryan S J, editors. Medical and Surgical Retina. St. Louis; Mosby, 1994; 330-340). In previous experience, in addition to observation for two or three months to see whether the recurrent hemorrhage can be absorbed per se, there are two surgical methods to manage the recurrent hemorrhage, including: fluid-gas exchange method and vitreous cavity lavage method. In the fluid-gas exchange method, air is used to replace the bloody fluid in the eyeball, yet the intra-ocular pressure (IOP) cannot be maintained constant during the procedure such that the oozing rate is rather high. In addition, when air bubble presents in the vitreous cavity, the patient sees nothing; when the air bubble disappears, the recurrent hemorrhage often results again from the oozing due to fluctuation of the intra-ocular pressure. Thus, the fluid-gas exchange cannot offer useful vision immediately after the procedure.
The conventional vitreous cavity lavage method, although having the potential to improve vision immediately after the procedure, still has two drawbacks: unstable IOP and the necessity of the larger caliber needle. The drainage needle, although of larger caliber, cannot aspirate the bloody fluid actively. In addition, although the caliber of the drainage needle could be rather large, the drainage needle still tends to be blocked by a blood clot or residual vitreous fiber. The procedure of vitreous lavage will thus be interrupted. Meanwhile, larger drainage needles induce larger wounds, more trauma, and higher incidence of recurrent hemorrhage.
The present invention is intended to provide an apparatus which mitigates and/or obviates the above problems.